I use UbuntuStudio 8.04 (Hardy Heron) with Intel Dual Core, 6gb RAM, 64-bit.
My computer is compiled at a Computer Fair (I've done my homework - informing myself about Alsa supported soundcards and bought the HDSP 96/32 soundcard and a compatible video-card).
In April 2008 I downloaded 5 recommended audio distro's - Only UbuntuStudio 8.04 worked out of the box for me.
I use it for professional work.
The distro is stable, solid (skype works well - I have used it in the past)
I use the installed software, adding some minor pieces (Rakarrack, Qsynth and Qtractor upgrades, etc)
I am extremely satisfied - never had a system crash or any unusual issues.
I use Ardour (and lately Qtractor), Rosegarden, Hydrogen, Rackarrack, Jamin, Qsynth, ZynAddSubFx - all at the same time, recording up to 20 audio and many midi channels, plugins - no issues at all.
Viktor